Electromagnetic switching device



May 17, 1938. R WOODLAND AL 2,117,531

ELECTROMAGNETIC SWITCHING DEVICE Filed Sept. 16. 1935 FIG.

l N VEN TORS CR. WOODLAND C. RHODES A TTORA'EY.

Patented May 17, 1938 UNITED STATES PATENT OFFICE ELECTROMAGNETICSWITCHING DEVICE Application September In Great Britain 3 Claims.

The present invention relates to electromagnetic switching devices andis more particularly concerned with devices which are adapted to respondto momentary pulses of signalling current and thereby produce differentcircuit changes in accordance with the number of pulses received. Oneapplication of such an arrangement is in connection with systems forremote control over public supply mains and the chief object of theinvention is to provide an improved switching device which will enablediflerent control operations for example, street lighting, shop windowlighting and meter tariiT change to be effected over the same circuit.The system is arranged so that the switching devices for the variouspurposes will operate from certain number of pulses only and no others,the numbers chosen being difierent for each kind of control. Clearly ifthe signal pulses are all of the same kind and diiler only in number,then all switching devices will respond together, but it will beappreciated that only those which have the corresponding setting will beable to perform their circuit changing function in response to aparticular train of impulses. In cases such as this where large numbersof switching devices are to be operated in synchronism, it is importantthat they shall not get out of step with each other, and it is a furtherobject of the invention to provide that if this should occur the devicesshall automatically correct themselves dur ing subsequent operations.

According to the invention an electromagnetic device for effectingswitching operations in response to predetermined numbers of impulses ofsignalling current is arranged so that the impulses efiect the rotationof an operating member which returns to normal at the end of the trainof impulses and thereupon operates a switching member to produce circuitchanges if the impulse train comprises the predetermined number ofimpulses.

The invention will be better understood from the following descriptionof one method of carrying it into effect, which should be taken inconjunction with the accompanying drawing comprising Figs. 1 and 2 whichshow side and front views respectively of an electromagnetic switchingdevice according to the invention.

In the description which follows it is assumed that the switching deviceis to be operated in a local circuit under the control of a sensitiverelay which responds to pulses of high frequency current superimposed onpublic supply mains in the manner described in the application of Philip16, 1935, Serial No. 40,694 September 25, 1934 N. Roseby, Serial No,4646, filed 2nd. February 1935. The invention however is not limited tothis type of control and the device could also be operated directlyeither by pulses of the type considered or by pulses transmitted fromthe sending point in an independent circuit. The device illustrated issuitable for responding to pulses of alternating current at the supplyfrequency.

Referring to Fig. 1, the electromagnet which responds to the impulsescomprises a spool l0 supported on one limb of a U-shaped laminated coremember I l, the other limb of which lies behind the side plate l2 towhich the armature is is pivoted. In order that the magnet shall respondreliably to alternating current, it is provided with what is known as ashaded pole formed by slitting the core adjacent to the armature andencircling one portion with a copper collar 24 as shown in the drawing.When the magnet is energized from the pulses it acts on a block oflaminations riveted to the armature thereby causing the armature to beattracted and released in synchronism with the pulses. Pivoted to thefree end of the armature is a spring loaded pawl 14 shown more clearlyin Fig. 2 which serves to rotate the ratchet wheel 15 step by stepagainst the return spring 15. Part of the return spring 16 which isapproximately twice the length visible is accommodated in a hollowed outportion of the ratchet wheel 15. Ratchet wheel 15 is rigidly attached toratchet wheel I1 and both revolve on a fixed shaft [8 supported in thearms of a U-shaped mounting bracket l9 secured to the base plate 20. Afurther arm of bracket 19 carrying an adjusting stop 39 for the armatureM which will be described later is conveniently shown broken away inFig. 2 to expose the driving mechanism. It will also be seen from thisfigure that the armature I3 is provided with a pair of short arms 3'!and 38 bent out at right angles on opposite sides, the one on the right31 engaging with the armature restoring spring 2i and detent spring 22shown in Fig. 1, while the one on the left 38 is forked and engages withthe collared head of the air dash-pot 23. The function of the dash-potis to retard the full release of the armature and so prevent the ratchetwheels returning to normal between pulses as will be described.

On the first attraction of the armature the ratchet wheels 15 and H arerotated one step and the detent spring 22 is lowered into engagementwith the ratchet wheel ll so that the lug 25 on the spring 22 seatsitself behind the appropriate tooth on the wheel. Simultaneously withthis operation. the dash-pot 23 is depressed to the full. extent. Uponthe de-energization of the magnet at the end of the first pulse, thearmature releases quickly at first under the infiuence of the restoringspring 2i until its forked arm comes up against the head of the dash-potplunger and thereafter further release is impeded by the drag of thedash-pot. By suitable adjustment it is arranged that the second andsubsequent pulses are received before the armature has movedsuffi-ciently far to lift the detent 25 on spring clear of the ratchetwheel i? and accordingly pulses are stored on the ratchet wheels whichare advanced to a characteristic po sition.

At the end of the pulse train the armature has sufficient time toovercome the drag of the dash-pot and when it has fully released, thedetent 25 on spring 22 is lifted clear of the ratchet wheel I? whichthereupon restores to normal under the influence of the restoring springl6. Pivoted to the ratchet wheel i1 is a wide detent 26 shown moreclearly in Fig. 1 which bears against the face of cam 27 which isrigidly secured to the contact operating cam 28. Cam 2 is provided withnotches around its face suitably spaced in accordance with the numberand sequence of the impulses to which the device is to respond while cam28 may be shaped as shown with a slow lift face suitable for comtrolling the contact springs 29. Only one set of springs has been shownin the drawing but it will be understood that others may be provided inaccordance with the control required.

The effect of the impulsing operation therefore is to advance ratchetwheel H to a predetermined position where the detent 26, which itcarries, engages with a notch in the cam 21 and, upon release due to thewithdrawal of detent 22, the two cams are rotated together to controlthe operation of the contact springs.

In a mixed system of the type suggested it may be arranged for example,that 2 and 3 impulses respectively will switch shop window lights on oroff 4, 5, and 6 impulses will serve for the graduated control of streetlights, that is, one lamp on, two lamps on, and both off while '7 and 8impulses will control the meter tariff change at consumers premises.

The switching devices for the various control systems are therefore setby these impulses and although all devices respond simultaneously, onlythose which have the characteristic setting will be able to performtheir circuit-changing functions. For this purpose the detent 26 iscontrolled from the double-armed swash plate 30 which is friction tighton the fixed shaft I8, being pressed against the side of the mountingbracket is by means of a fiat spring 3| secured to the bracket by thescrews 32. During the forward stepping motion the swash plate Bil ispushed round by contacting with the upper edge (in the position shown)of the detent 26 and owing to the peculiar shape of the latter it isautomatically tilted into engagement with the cam 21. Accordingly afterthe correct number of impulses have been received, the detent is tiltedinto a notch on the cam 21, and upon release the cams and swash plateare carried back to the normal position which is determined by thecurved back of the detent coming up against a correspondingly curvedface on the frame member ii If however, the number of impulses receivedis in excess of the number allocated for the system in which theparticular switching device is located, the detent 26 is carried pastthe notch in the cam 2'! and upon release the rear edge leaves the swashplate and the front edge comes up against the other arm of the swashplate to drive it back to the normal position. It will be noticedhowever, that owing to the inclination of the other arm of the swashplate the detent becomes trapped and is prevented from entering thenotch in the cam during the return movement.

If less than the predetermined number of impulses are received, thedetent 26 will obviously fail to reach the notch in the cam 27! and theswitch therefore restores without producing any change in the conditionof the contact-controlling cam 28.

If at any time the switches should get out of step owing to thereception of a false set of pulses which operate some devices and notothers it will be appreciated that the next set of pulses which appliesto the devices of that switching system will bring them all into line.This feature is particularly important in the case of large networkssince otherwise each individual switch may have to be visited andcorrected.

Considering now the various operating details of the mechanism not yetdealt with, it will be seen that the normal position of the armature i 3is regulated by the angle-shaped back stop 33 which is fastened to thefront arm of the mounting bracket i9 and is capable of verticaladjustment thereon by the screw and slot shown in Fig. 2. The fullyoperated position of the armature is regulated by the pawl i i jammingagainst a front stop comprising an adjusting screw 39 threaded throughthe bracket member iii. The normal position angle of the spring-loadedpawl M is adjusted by bending the tongue 34, which is a part of the tailpiece of pawl M and which rests against the underside of the armature,until the pawl 14 is directed towards a tooth on the ratchet wheel i5.In the normal position the cams 2'! and 28 are prevented from movementby the locking effect of the pawl 26 but in order to prevent theirmovement during the setting operation of the pawl, the moving spring ofthe contact pair 29 is provided with a notch as shown which is engagedby the tooth of cam 23 and introduces a slight locking effect,sufiicient to prevent the movement of the cams owing to vibration or thefriction of the detent 26 moving over the operating face. Theairdash-pot is' of the type employing a solid graphite plunger which istherefore self-lubricating and enjoys a long life.

The whole unit described is secured in a suitable manner to the mountingplate 35 preferably composed of insulating material of the syntheticresin type and is enclosed in a dust cover (not shown) of similarmaterial. The electrical connections to be made external to the unit areled out to spring pins 36, the fixing for which passes through a hole inthe mounting plate and is rigidly fastened thereto. Four such pins arepro vided to carry circuits for the operating coil and contact springsand these pins are adapted to register with sockets in a mounting frameand are suhiciently robust to hold the unit in its mounted positionwithout the necessity for any other supporting brackets or attachments.Details of the mounting arrangements and dust cover are not shown in thedrawing, but they follow the same general lines as in the case of theunit described in the application of Cecil R. Woodland, Serial No.758,573, filed 21st December 1934.

We claim:

1. An electromagnetic circuit-closing device for effecting circuitchanges, comprising a ratchet wheel, a spring, a detent carried by saidwheel, a notched cam, means for rotating said wheel against the tensionof said spring, and then releasing it, a friction element on said wheel,said element engaging said detent and causing it to engage a notch insaid cam when the wheel is rotated a predetermined number of steps, saidspring operating the wheel and cam together on release when the detentengages a notch, such element engaging said detent and holding it out ofengagement with the notches of said cam when the wheel is rotated otherthan the predetermined number of steps, said spring returning said wheelto normal without operating the cam if the detent is moved past a notchby the wheel.

2. An electromagnetic device comprising switching springs, a cam foroperating said springs having notches therein spaced at unequalintervals around the cam, a ratchet wheel, a magnet having means forrotating and releasing the wheel, a detent on the wheel moved therebyinto position to engage a notch in the cam, a

spring for moving the wheel and cam through the medium of the detentwhen the wheel is released, said magnet responsive to a predeterminedseries of impulses to cause the cam to engage one notch and responsiveto another predetermined series of impulses to engage a second notch,and a friction element between the cam and wheel having one partengaging the detent to cause it to engage a notch in the first instanceand another part preventing the detent from engaging a notch in theother instance.

3. An electromagnetic switching device comprising a ratchet wheel, amagnet for rotating the wheel and releasing it, a detent carriedbackward and forward by the wheel, a notched cam adjacent the Wheel andhaving notches spaced at varying distances on its periphery engageableby said detent, a friction element associated with the detent, a pair ofprongs on the element in the path of said detent, one prong of theelement engaged by the detent on its forward movement to cause thedetent to engage the periphery of the cam, and the other prong of saidelement engaged by the detent on its backward movement to preventengagement of the detent with the periphery of the cam.

CECIL ROBERT WOODLAND. CECIL RHODES.

